Inter Milan and Roma were forced to settle for a share of the spoils with respective draws against Sampdoria and Atalanta, meaning leaders Juventus could pull clear of the pack later Sunday.
Inter looked to have secured their seventh win of the season after Fredy Guarin had given the Nerazzurri an 18th minute lead at the San Siro.
However Sampdoria, now under the helm of former midfielder Sinisa Mihajlovic, came fighting back and stunned the hosts when Brazilian midfielder Renan beat Samir Handanovic with a shot from distance.
Inter's sixth draw of the campaign and second in a row left Walter Mazzarri's men in fourth, just three points ahead of Fiorentina, who host Verona on Monday, and in danger of trailing Juventus by 10 points if the champions beat Udinese in Sunday's late game.
"It's the worst game I've seen us play since I've been in charge," blasted Mazzarri in comments to Sky Sport Italia.
"After taking the lead we had several chances to put it beyond reach. But Sampdoria gave it everything and were better than us. I didn't like what I saw from Inter."
Early season pacesetters Roma had the chance to regain top spot but instead Rudi Garcia's men were made to work for what was their fourth consecutive draw.
Atalanta broke the deadlock when Roma goalkeeper Morgan De Sanctis fumbled Davide Brivio's freekick to gift the Bergamo side a 51st minute lead.
Roma recently set a new Serie A record of 10 opening wins but had drawn their last three outings, including a disappointing scoreless affair at home to struggling Cagliari last week.
After Atalanta keeper Andrea Consigli denied both Alessandro Florenzi and Gervinho from close range in the final 10 minutes, Roma grabbed a welcome point when Dutch midfielder Kevin Strootman fired home a last minute equaliser.
Roma had been denied a late claim for a penalty when the ball appeared to come off Michele Canini's arm and Garcia told Mediaset: "It's better I don't talk about it but everyone saw it."
The Frenchman added: "If we had played the whole match as we did in the final half hour, we wouldn't need to rely on wrong decisions from the referee."
Roma's latest slip has paved the way for Juventus to pull three points ahead and given third-placed Napoli, who are away to Lazio on Monday, the chance to close the gap on Roma to three points.
Earlier, Mario Balotelli scored his first league goal in over two months as struggling Serie A giants AC Milan secured a precious 3-1 win away to 10-man Catania.
"It's a great victory for us and has given us confidence, we're coming off the back of four positive results, one in the Champions League and three in the league," said Milan coach Massimiliano Allegri, whose side moved up to ninth.
Catania, who were reduced to 10 men just after the hour when Panagiotis Tachtsidis saw red for a foul on Balotelli, started brightly and took the lead on 13 minutes when a shot by Lucas Castro deflected off Antonio Nocerino and wrong-footed Gabriel in the Milan net.
Captain Riccardo Montolivo levelled for the visitors shortly after with a splendid first-time strike from a cross deep on the left.
Balotelli, who scored for Milan in a resounding 3-0 Champions League win away to Celtic in midweek, finally ended his Serie A goal drought when he beat Mariano Andujar with a freekick on 63 minutes. It was his first league goal since a late consolation in a 2-1 defeat at home to Napoli on September 22.
Kaka secured the points when he beat Andujar with a fine individual effort nine minutes from the final whistle.